Effect of radiotherapy after breast-conserving surgery in elderly patients with early breast cancer according to the AJCC 8th Edition Breast Cancer Staging System in Japan

Background: The number of elderly patients in Japan with breast cancer has been gradually increasing. The aim of this study was to determine the efficacy of radiotherapy (RT) after breast-conserving surgery (BCS) for elderly patients with early breast cancer who were restaged according to the 8th Edition Breast Cancer Staging System. Methods: We reviewed patients age ≥ 65 years who received BCS and adjuvant RT or BCS alone for breast cancer between 2010 and 2015 in our institution and restaged those patients using the AJCC 8th edition pathological prognostic staging system. We compared relapse-free survival (RFS) and overall survival (OS) rates in the RT group and no RT group. Results: A total of 170 patients were eligible for analysis: 94 (55.3%) were treated with RT and 76 (44.7%) were treated without RT. Age (p < 0.01) was associated with the use of RT. Adjuvant RT significantly improved RFS (95.75% vs 84.21%, p = 0.02). There was no significant difference between the OS rates in the two groups. Univariate analysis showed that pathologic T stage and N stage were significantly associated with both RFS and OS and that histologic grade, chemotherapy, HER2, and RT were significantly associated with RFS, but not with OS. RT reduced the risk of recurrence (HR = 0.56, 95% CI = 0.19–0.96, p = 0.04). Conclusions: RT was associated with significantly improved RFS, but had no significant impact on OS in elderly patients with breast cancer after BCS. Adjuvant RT should be performed even for elderly patients with early breast cancer.